I replaced the MOSFET with the MPSA42 I'm using, and the circuit seems to work in spice, switching at about 40 kHz and with an open-circuit output voltage a bit above 80 V. I'd like to breadboard it and need advice on a suitable PNP to use. Here's a plot of the voltages seen by the PNP: **broken link removed**
Node 2 is the emitter, 1 is base and 5 is collector. Those Vbe spikes up to the full output voltage look a bit worrisome. Would a suitable high-voltage PNP BJT tolerate them?
Edit: this circuit has awful efficiency and is of no practical interest. Sorry for the noise.